Validation of a rapid, conservative transuranic alpha activity estimation method in air samples.

Area of Science:

• Environmental Science
• Radiological Monitoring
• Nuclear Chemistry

Background:

• Radon (Rn-222) and thoron (Rn-220) progeny are significant interferents in estimating transuranic (TRU) activity from air samples.
• Accurate TRU activity estimation is critical for radiological emergency response and environmental monitoring.

Purpose of the Study:

• To validate a rapid, conservative, and defensible methodology for estimating TRU alpha activity in air filters.
• To assess the impact of radon and thoron progeny on TRU activity measurements.
• To verify a previously developed graded approach for TRU activity estimation.

Main Methods:

• A conservative, graded approach was applied to air samples containing radon and thoron progeny.
• Surrogate transuranic activity (Pu-239 and Th-230 check sources) was introduced to environmental air filters.
• Filters were center hole-punched with check sources placed underneath during counting.
• Blank filters were used to characterize surrogate source activity without environmental interferents.

Main Results:

• The validated methodology demonstrated quantifiable conservative bias in TRU activity estimation.
• 70 environmental filters with varying radon progeny levels and sampling durations were analyzed.
• 35 filters were tested with Pu-239 check sources and 35 with Th-230 check sources.
• The method proved effective in providing rapid and conservative TRU activity estimates.

Conclusions:

• The study successfully validated a rapid and conservative method for TRU alpha activity estimation in air filters.
• This methodology accounts for natural radioactive progeny interferents, enhancing the reliability of radiological emergency response assessments.
• The findings contribute to the comprehensive analysis of operational air samples for accurate TRU activity determination.